Many conventional fluid dispensing devices utilize electronic valves or pinch valves together with some type of flexible tubing, such as silicon tubing, to dispense a predetermined volume of a fluid into a receptacle. For example, one such device currently in use is known as a time/pressure filler. Generally, time/pressure fillers dispense a predetermined volume of fluid from a reservoir through a compressible tube enclosed in a pinch valve. Particularly, the pinch valve is energized causing it to open for a predetermined period of time to dispense the fluid into a receptacle, and then de-energized causing it to close for another predetermined period of time to cease dispensing the fluid into the receptacle. Assuming that the pressure within the fluid reservoir remains constant, an equal volume of fluid should be dispensed into the receptacle each time the dispensing “cycle” (i.e., the energizing/opening and de-energizing/closing of the pinch valve) is repeated.
A second type of fluid dispensing device is known as a volumetric fluid dispensing device. These types of fluid dispensing devices first measure a predetermined volume of fluid using one or more optical sensors, for example. More particularly, the fluid flows from a fluid reservoir and into a fill tube that holds a premeasured volume of fluid. The sensors, which may be proximate the fill tube, detect the level of fluid in the fill tube and generate signals indicating those detected levels to a processor. The processor, in response to those signals, then controls a pinch valve with the compressible tubing to open and close thereby controlling the flow of fluid into and out of the fill tube.
Another type of fluid dispensing device is known as a Time Dispense device. These types of dispensing devices are similar to the volumetric fluid dispensing devices. However, rather than premeasuring a volume of fluid to be dispensed using one or more sensors, Time Dispense devices control the valves using a timer. Specifically, these devices dispense a fluid by opening and closing a dispense valve for specific predetermined periods of time. While the valve is opened, the fluid flows into a waiting receptacle until the dispense valve is closed.
Each of these of fluid dispensing devices has advantages, such as speed and/or volume. However, each also has a tendency to cause variances in the volumes of fluid dispensed.